The object of this work is to determine how much volume of the cytoplasm is occupied by the cytoplasmic matrix under different external osmotic environments, and how it affects the diffusional motion of proteins inside the cytoplasm. The cytoplasmic matrix is composed of the microfilaments, intermediate filaments, microtubules and the microtrabecular lattice. We developed and image analysis method to study the volume and surface area of the cytoplasmic matrix. The low values (10%-30%) obtained for the fractional volumes indicate that by excluded volume alone, the cytoplasmic matrix cannot slow down the diffusion of proteins to such an extent as compared with the diffusion in water. Analysis showed that binding of the diffusing proteins to the cytoplasmic matrix could explain the results. The values of the binding constants obtained point out that although the association - dissociation process can occur very fast, at any given time, most of the proteins may be bound to the cytoplasmic matrix. We have initiated the study of the effect of the external osmotic environment on the fractional volume of the cytoplasmic matrix in the cytoplasm. The surface area attributed to the cytoplasmic matrix was calculated to be in the range of 43,000 - 140,000 m2 per cell. The meaningfulness of this work lies in the fact that measuring the volume fraction of the cytoplasmic matrix can shed light on the physical and chemical constraints on molecular transport through the cytoplasm. The estimate of surface area associated with the cytoplasmic matrix is important in understanding the role of hydrated water on macromolecular surfaces in the physiology of the cell.